1. Field of the Invention
The invention disclosed in this specification and the like relates to a sealed body and a method for manufacturing the sealed body. In particular, the invention relates to a sealed body (a semiconductor device) internally including a semiconductor element.
In this specification and the like, a semiconductor device refers to all types of devices which can function by utilizing semiconductor characteristics; an electro-optical device, an image display device, a semiconductor circuit, and an electronic appliance are all semiconductor devices.
2. Description of the Related Art
As a method of enclosing an element between a pair of facing substrates, a technique in which substrates are bonded to each other using powdered low-melting-point glass (also referred to as glass frits) as a sealing material to form a sealed body with a high sealed property is known.
Such glass frits have a high barrier property; thus, a sealed space can be kept away from the external atmosphere. The method of sealing with glass fits has been applied to, for example, a device including a semiconductor element such as an organic electroluminescence (EL) element, an organic semiconductor element, an organic solar cell, or a liquid crystal element.
In the method of sealing with glass frits, in general, the following steps are performed: a sealing member containing glass frits made of low-melting-point glass and a binder is applied along a rim of a glass substrate; the sealing member is baked to reduce or remove the binder; the glass substrate is overlapped with a counter substrate; the sealing member is irradiated with laser light to melt the glass fits contained in the sealing member, so that a sealing layer is formed; and the glass substrate and the counter substrate are welded, so that a sealed body with high airtightness is formed,
In laser light irradiation, the laser light is absorbed in or reflected by a wiring layer in a region where a sealing member and the wiring layer (electrode) overlap; thus, the energy of laser light which is needed for welding is different from the energy of laser light which is needed for another region (i.e., a region where the sealing member and the wiring layer do not overlap). When the sealing member in the overlap region is irradiated with excess energy due to reflection of the laser light by the wiring layer, the adhesion between the sealing member in the region and the substrate is reduced. Furthermore, in some cases, the wiring layer is deformed or disconnected due to absorption of the laser light in the wiring layer.
Patent Document 1 discloses a sealing method in which a reflective mask is provided in a region which is over a counter substrate and overlaps with an electrode so that the region is irradiated with lower energy of laser light.